This invention relates to a positioning control device of a head. More particularly, it relates to positioning a head to a data track of a disk such as a magnetic disk device or an optical disk device and the likes.
In the below, a conventional magnetic head and a prior-art magnetic disk device are described in detail by way of examples in case of a head and a disk device as claimed.
Heretofore, a prior-art magnetic disk device of a memory used, for example, in a computer and the likes is configured as shown in FIG. 1. In FIG. 1, numeral 1 designates a magnetic disk, and information is recorded on tracks arranged concentrically at a predetermined interval. Numeral 2 designates a spindle motor for rotating the disk 1 at a predetermined speed. Numeral 3 designates a magnetic head for reading/writing information in the tracks of the disk 1. Numeral 4 designates an actuator for moving the head 3 by the drive force of a positioning stepping motor 5 (STM) to position the head 3 on an arbitrary track. Numeral 6 designates a base for fastening the motor 2, the actuator 4 and the motor 5. Numeral 7.sub.PA designates an index sensor for detecting the index of the rotating section of the motor 2 and outputting an index signal at the beginning of a revolution.
The circuit arrangement of the magnetic disk device thus configurated as described above is now described by referring to FIG. 2.
In FIG. 2, numeral 8 designates a positioning control device (PCD) for outputting a drive signal B for rotating the motor 5 when receiving a head movement command signal A from a controller and outputting a positioning completion signal Z when the head 3 is completely moved to the track position where it is to be positioned. Numeral 9 designates a driving amplifier device (DAD) for amplifying the drive signal B, rotating the motor 5 by the drive power D and setting the stopping angle of the motor. Thus, the head 3 is positioned on the track of the disk 1. When the index sensor detects an index and the index detection signal is received by an external circuit (not shown), the head can read/write information on the corresponding track of the disk 1.
Environmental temperature varies and since the temperature expansion coefficients and the likes of the disk 1, the actuator 4 and the base 6 of the positioning control device of the prior-art disk apparatus are different from each other, the track on the disk 1 is relatively displaced from the position of the positioned head 3, an interference between the magnetisms produced by the adjacent tracks occurs, and the reliability in reading/writing information on the tracks by the head deteriorates. Such a problem creates difficulties in increasing the density of the track to increase the total number of tracks on the disk.